This invention relates generally to pumps for hydraulic systems. More particularly, this invention relates to pumps with throttle valves for hydraulic fuel systems in internal combustion engines.
Many internal combustion engines use hydraulically-activated electronically-controlled unit injection (HEUI) fuel systems to improve engine performance. HEUI fuel systems require high pressure hydraulic fluid to operate fuel injectors. FIG. 4 shows a hydraulic system according to the prior art. The hydraulic system is for an engine with a V-configuration and has a high pressure side incorporated with a low pressure side. The high pressure side operates the fuel injectors. A high pressure pump provides hydraulic fluid from a low pressure reservoir through an injection pressure regulation (IPR) valve to high pressure reservoirs. The low pressure side provides lubrication for various components of the engine including a cylinder head, cylinders, pistons, a turbocharger, and the like. A low pressure pump provides hydraulic fluid from a sump to the low pressure reservoir and to the engine. The hydraulic fluid passes through an engine cooler and an oil filter. The high and low pressure sides have other components such as check and bypass valves, which are not shown.
During engine operation, the IPR valve and high pressure pump control the volume and pressure of the hydraulic fluid. The IPR valve controls the pressure of the hydraulic fluid to be in a range of about 500 psi through about 6,000 psi. The IPR valve typically reciprocates between open and closed positions to maintain or regulate pressure. An open position dumps high-pressure hydraulic fluid from the high pressure pump. A closed position does not dump hydraulic fluid. When higher pressure is required, the IPR valve closes or reciprocates more in a closed position. When lower pressure is required, the IPR opens or reciprocates more in an open position to dump hydraulic fluid.
In addition, the high pressure pump adjusts the volume of hydraulic fluid depending upon the operating requirements of the engine. FIG. 5 shows a side view of a high pressure pump according to the prior art. A support shaft, bearing shaft, and drive shaft are radially aligned and disposed inside a pump housing. A bearing spring biases a slipper plate against a spherical bearing mounted on the bearing support. Several cylinders are disposed radially around the support shaft. A piston is disposed within each cylinder. Each piston is pivotally connected to the slipper plate. The drive shaft has a swash plate, which engages the slipper plate. The swash plate sits at an angle to the cylinders.
As the drive shaft rotates, the swash plate pushes pistons into the cylinders on one side and pulls or lets the pistons out of the cylinders on the other side. A complete rotation of the drive shaft causes each piston to reciprocate one stroke in the cylinder. Hydraulic fluid from the low pressure reservoir enters a low pressure inlet along the outside of the pump housing. A valve controls the amount of hydraulic fluid exiting a valve outlet into an oil feed chamber, which surrounds the cylinders. The oil feed chamber has a cylinder inlet into each cylinder. As the piston reciprocates toward the swash plash, the piston passes the cylinder inlet. The cylinder inlet opens and hydraulic fluid fills the cylinder. As the piston reciprocates away from the swash plate, the cylinder inlet closes and the piston pushes the hydraulic fluid against a vent plate in the cylinder. The vent plate eventually opens permitting high pressure hydraulic fluid to enter a discharge chamber. The hydraulic fluid accumulates in the discharge chamber until it exits the high pressure pump through a high pressure outlet. A retention plate prevents the backflow of hydraulic fluid into the cylinder from the discharge chamber.
Generally, the high pressure pump provides more hydraulic fluid when higher pressure is required and provides less hydraulic fluid when lower pressure is required. The valve typically closes when there is a need for less hydraulic fluid. However, there may be a lag period between the time the lower volume is needed and the time the valve closes. Hydraulic fluid in the oil feed chamber generally passes through the pump, is pressurized, and is dumped. The oil feed chamber may hold up to 0.75 liters of hydraulic fluid.
The dumping of high-pressure hydraulic fluid reduces engine efficiency and increases operating costs. While a single xe2x80x9cdumpingxe2x80x9d of hydraulic fluid may be less significant, the accumulated dumping of hydraulic fluid may reduce engine efficiency in a range of about 5 percent through about 15 percent. The reduced efficiency increases fuel consumption and may increase the maintenance of the engine.
This invention provides a pump with a close-mounted valve for a hydraulic fuel system in an internal combustion engine. The close-mounted valve may be used to control the hydraulic fluid volume and the hydraulic fluid pressure. The close mounted value also may be used with or without an injection pressure regulation (IPR) valve. The close-mounted value may reduce or eliminate the need to dump high-pressure hydraulic fluid in a hydraulic fuel system.
In one aspect, a hydraulic fuel system for an internal combustion engine has a high pressure pump connected to a low pressure side and one or more high pressure reservoirs. The high pressure pump has a drive shaft, a shaft cylinder, one or more cylinders, and a close-mounted valve. The shaft cylinder is aligned with the drive shaft and forms a shaft cavity. One or more cylinders are positioned next to the shaft cylinder. The cylinders have one or more cylinder inlets into the shaft cavity. The close-mounted valve has a valve body, a valve spool, a valve spring, and a valve coil. The valve body is positioned inside the shaft cavity. The valve body forms a valve cavity having one or more valve outlets corresponding to the one or more cylinder inlets. The valve spool has an armature and is positioned inside the valve cavity. The valve spring is positioned between the armature and the valve body to bias the valve spool. The valve coil positioned along the valve body and around the armature.
In another aspect, a pump for a hydraulic fuel system in an internal combustion engine has a drive shaft, a shaft cylinder, one or more cylinders, and a close-mounted valve. The shaft cylinder is aligned with the drive shaft and forms a shaft cavity. The one or more cylinders is disposed adjacent to the shaft cylinder. The cylinders form one or more cylinder inlets into the shaft cavity. The close-mounted valve is positioned in the shaft cavity and has a valve body, a valve spool, a valve spring, and a valve coil. The valve body forms a valve cavity having one or more valve outlets corresponding to the one or more cylinder inlets. The valve spool has an armature and is positioned in the valve cavity. The valve spring is positioned between the armature and the valve body to bias the valve spool. The valve coil is positioned along the valve body and around the armature.
Other systems, methods, features, and advantages of the invention will be or will become apparent to one skilled in the art upon examination of the following figures and detailed description. All such additional systems, methods, features, and advantages are intended to be included within this description, within the scope of the invention, and protected by the accompanying claims.